KR19980013717A - Driving Method for Display Apparatus - Google Patents

Abstract

A pair of electrodes, and a light modulating device comprising a photoconductive layer and a layer of optical modulator material between the electrodes, a signal light source for supplying optical data for carrying grade data to the photoconductive layer, A readout light source for supplying readout light to the layer of optical modulators to provide a readout light. Wherein the display device scans and supplies the optical data to the photoconductive layer; And scanning and supplying the readout light to the layer of optical modulators. Preferably, the illumination time of the read-out light source is controlled to modulate an overlap period between the duration of the light modulating material having a defined optical state and the illumination time in accordance with a given grade data.

Description

Driving method for display device

The present invention relates to a method, an apparatus or a system for driving an optical modulation or image display apparatus or a unit which emits from a light source or controls the amount of light transmitted or reflected by a light source.

The light modulation device is included in various optical devices such as a display device. For example, in accordance with various methods to be described below with respect to a liquid crystal display device as a similar example, a gradation display or a gray-scale display is performed using an optical modulation device.

According to one method, a twisted nematic (TN) liquid crystal is used as an optical modulation element (material) constituting a pixel and voltage data is applied to a TN liquid crystal to modulate (control) ).

According to the second scheme, one pixel is composed of a plurality of sub-pixels assembled so that each sub-pixel is turned on or off based on the binary data to modulate the area of the sub- Off. This method is disclosed, for example, in Japanese Patent Application Publication Nos. JP-A 56-88193 and European Patent Application Publication Nos. EP-A 453033 and EP-A 361981.

According to the third scheme, a bright state portion and a dark state portion coexist in various region ratios to adjust the electric field intensity of liquid crystal in one pixel so as to modulate the transmittance through the pixel. Or variance of the inverse threshold is provided. This scheme is given to Kaneko and is described in U.S. Patent No. 4,796,980 entitled " Ferroelecthc Liquid Crystal Light Modulating Device Having Area Within a Pixel to Initiate Nucleation and Reversal " and U.S. Patent Nos. 4,712,877, 4,747,671 No. 4,763,994, and the like.

According to the fourth scheme, the period of one pixel indicating the light state is turned on to modulate.

This method is disclosed in U.S. Patent No. 4,709,995, entitled " Ferroelectric Display Panel and Display Method ", which is granted to Kuribayashi et al. And activates gray scale.

Another example of digital duty modulation is disclosed in U.S. Patent No. 5,311,206 issued to Nelson and entitled Active Line Backlight Thermal Shutter LCD with one shutter transition per row have.

Here, the first scheme relates to luminance modulation, the second scheme corresponds to pixel division, the third scheme corresponds to area modulation, and the fourth scheme relates to digital duty modulation.

The luminance modulation is not easily applied to an apparatus using a light modulating material having a sharp transitional change characteristic or a memory characteristic. Also, since the TN-liquid crystal has a usually slow response speed, it is impossible to apply it to a system that processes data changing at high speed.

Pixel partitioning, which is equivalent to a system using unit pixels that include assembling pixels, has a low spatial frequency and is likely to have a lower resolution. Also, the optical interrupting portion (hght-interrupting portion) is increased to lower the aperture ratio.

Domain modulation requires pixels of complex structure that provide dispersion of the electric field intensity or inverse threshold. In addition, since the voltage margin of the halftone display is narrow, it is easily influenced by the temperature.

In digital duty modulation, the modulation unit time depends on the clock pulse frequency and the gate switching time

It requires on-off time modulation. Therefore, it is difficult to perform high-precision modulation and the number of displayable level levels is limited. In addition, this method necessarily requires analog-digital (A / D)) conversion of analog data, and thus can not be easily applied to a simple optical modulation system.

In view of the above problems, it is an object of the present invention to provide an optical modulation or image display system (i.e., a method and apparatus) that enables optical modulation based on analog data.

It is another object of the present invention to provide an optical modulation or image display system that can be applied to a light modulation device using a light modulation material having abrupt applied voltage-transimitance (V-T) characteristics with memory characteristics.

It is still another object of the present invention to provide an optical modulation or image display system capable of realizing high spatial frequency and high resolution.

It is another object of the present invention to provide graded data generation in a relatively simple manner based on analog duty modulation to provide an inexpensive optical modulation or image display system.

According to the present invention, there is provided a liquid crystal display comprising: a pair of electrodes; a light modulating material layer positioned between the electrodes; and a signal light source for providing optical data for conveying the grading data to the light conducting layer, And a reading light source for providing the light to the light source.

The driving method includes: providing optical data to the photoconductive layer in a scanning manner; And providing reading light to the layer of optical modulators in a scanning manner.

Preferably, the illumination time of the read-out light source is controlled to modulate the overlapping period between the period during which the light modulating material takes the prescribed optical state and the irradiation period according to the given grade data.

According to another aspect of the present invention, there is provided a light modulation device, comprising: (a) a light modulation element formed by positioning a layer of a light modulation material between a pair of electrodes and a driving element to provide an electric signal, (B) a light modulating device comprising a readout light source for providing readout light for reading the image data to the layer of optical modulation material, the method comprising: do.

The driving method includes: providing an electrical signal to a pixel selected by a scanning method; Scanning the pixel with readout light to provide readout light to the layer of modulator material at the selected pixel; And controlling the illumination period of the read-out light source to modulate the overlap period between the period of the light modulating material taking the prescribed optical state and the irradiation period according to the given grade data.

In the present invention, the time or period when the voltage applied to the light modulation element exceeds a threshold value necessary for switching the optical state of the light modulation element is changed in the analog mode depending on the given grade data. Consequently, the time integration of the amount of light modulated by the light modulation means, that is, the length of the overlapped period between the opening time of the optical shutter and the irradiation period of the light source, in the analog mode corresponds to the gradation data. Therefore, the number of rating levels is not limited by the digital amount such as the clock pulse frequency, and the (A / D) conversion of rating data can be omitted.

Analog modulation is also possible using a digital (or binary) display device with voltage-transmission characteristics, although the result is unpredictable yet steep.

Thus, a good grade display is possible according to the invention.

These and other objects, features and advantages of the present invention will become more apparent from the following description of the preferred embodiments of the invention taken in conjunction with the accompanying drawings. Respectively. First, however, a brief description of the basic system or principle to support the present invention is given below.

1 is a block diagram showing a basic configuration of an optical modulation system according to the present invention;

2 is a graph showing an applied voltage (or pulse width) dependent transmission characteristic of an optical modulation element (or material) used in the present invention.

3 is a timing diagram illustrating a basic embodiment of a method of driving an optical modulator according to the present invention.

4 is a diagram illustrating an embodiment for generating rating data used in the present invention.

5 is a block diagram showing another embodiment of an optical modulation system according to the present invention.

6 to 8 are diagrams of an embodiment of a driving circuit of an optical modulation device used in the present invention, respectively.

9A to 9D are graphs showing the transmittance-applied voltage characteristics of a light modulating material (or device) used in the present invention, respectively.

10 is a circuit diagram of a light modulation device;

11 is a time-seria1 waveform diagram illustrating a method of driving an optical modulator;

12, Fig. 14 and Fig. 16 are circuit diagrams of the optical modulation device, respectively.

Figs. 13, 15 and 17 are diagrams showing time-series waveforms used to drive the optical modulation devices of Figs. 12, 14 and 16, respectively. Fig.

18 is a schematic sectional view of an optical modulation device of an image display apparatus used in the present invention.

Figures 19A-19B are schematic illustrations of two molecular orientations (optical states) of a chiral smetic liquid crystal used in the apparatus of Figure 18;

20 is a graph showing electro-optical characteristics of a liquid crystal used in the apparatus of Fig.

Fig. 21 is a timing diagram for explaining the operation of the device of Fig. 18; Fig.

22 is a schematic explanatory view of an embodiment of an image display apparatus;

23 to 25 are timing diagrams for explaining the operation of the image forming apparatus according to the embodiment of the present invention, respectively.

26 is an example of a scanning method using writing light and reading light according to the embodiment of the present invention.

27 is an embodiment of a display device according to the present invention.

Fig. 28 is still another embodiment of a display device according to the present invention; Fig.

29 is a timing diagram for explaining an operation of the display device according to the present invention;

30 is an equivalent circuit diagram of an optical modulator in the embodiment of the display device according to the present invention.

31 is a schematic partial cross-sectional view of a portion corresponding to approximately one pixel of the light modulation device used in the present invention.

32 is a timing diagram illustrating an operation of the display device according to the present invention;

33 is an example of a scanning method using reading light.

FIG. 34 is a configuration example of a display device according to the present invention; FIG.

Description of the Related Art [0002]

810: CRT

811: image forming lens

812: Reset light source

815: available mirror

816: Filter

817: a reading light source

818: Lighting Lens

819: Image playback screen

906: gate electrode

907: bottom electrode

908: Gate insulating film

909, 910:

911: source electrode

912: drain electrode

914: channel layer

first. The basic modulation scheme adopted in the present invention will be described with reference to the drawings.

1 is a diagram of a system example for realizing a modulation scheme according to the present invention. The system includes an optical shutter 1 for controlling light transmission as optical modulation means, a light source 2 for emitting light, a drive means DRl for driving the optical shutter, a drive means DR2 for turning on and off the light source, And control means for controlling the power source of the driving means and the operating time of the driving means.

Fig. 2 is a graph showing an example of the transitivity change characteristic of the optical modulation element (material) constituting the optical shutter 1. Fig. For example, when the applied voltage of the constant pulse width exceeds the threshold value Vth. The transmittance rises rapidly and becomes a constant value at a saturation voltage (Vsat) or more. When the light modulating material has storage properties, the resulting optical state remains constant after the applied voltage is removed.

3 is a timing diagram illustrating the basic operation of the system shown in Fig. 3, curve 10 represents the optical transition of optical shutter 1, curve 20 represents the operation of light source 2 (light emission and non-light emission), curve 30 represents the amplitude ) Vop (and another optional pulse width PWop) is changed in accordance with any rating data.

The light source is to be the light is emitted from a light source for a period (t) set in advance to provide a halftone can be turned on and turned off at time t _3, the recognition between the time t _1.

Along with the periodic operation (light emission) of the light source, an applied voltage is supplied to the light modulating material and the dark state is switched from the dark state (Min) to the bright state (Max) when the time constant of the applied voltage exceeds the threshold value.

The rise time t ₂ of the switching depends on the amplitude Vop pulse width and the pulse width PWop. As at least one of the amplitude Vop and pulse width PWop is modulated according to data rates, the time t ₂ is to be changed in the time range (TM) according to the data rates.

The time t _off is a time for applying a call to turn off the light shutter. The time t _off is a time for which an amount of light transmitted through the optical shutter 1 is set at an overlap time between the irradiation time (period) , And this overlap time (period) is changed (modulated) in accordance with the rating data.

Consequently, the moment of the transmitted light amount can be easily modulated, for example, by changing the amplitude Vop in an analog manner at a constant pulse width PWop.

In the conventional digital duty modulation method, the application time t _on of the voltage signal 30 is changed in a digital manner with a constant pulse width PWop of the voltage signal 30 and an amplitude Vop.

In contrast, a new feature of the present invention is that the signal 30 is processed to an analog value having a varying amplitude (and / or pulse width) to enable analog duty modulation.

Fig. 4 shows an example of a circuit for generating an analog signal 30. Fig. Any gradation data is amplified by transistor Tr1 and sampled by switch transistor Tr2 to provide a modulated amplitude and a signal having a predetermined pulse width necessary to drive the optical shutter. In the example shown in Fig. 4, the amplifier Tr1 is composed of a bipolar transistor circuit, and the switch Tr2 is constituted by a MOSFET. However, the amplifier Tr1 and the switch Tr2 need not be limited to such simple devices.

Next, another basic modulation method will be described with reference to Fig.

The system shown in Fig. 5 is different from the system shown in Fig. 1 in that it includes light reflecting means 1A instead of the light transmitting means 1 shown in Fig. 1 as light modulating means. The light reflecting means may include a liquid crystal element or a mirror element. The reflective mode liquid crystal device is configured such that one of the pair of substrates sandwiching the liquid crystal is provided with a transmissive member and the other is provided with a reflective member so that a light-absorbing state or a light- To select the light-reflecting state. In the case of a mirror element, the mirror's reflection surface angle is controlled by the movement of the mirror so as to select a predetermined direction (ON state) suitable for reflection and another direction not causing reflection.

Next, the overlap time between the irradiation time of the light source 2 and the ON period of the reflecting means 2 is modulated in an analog manner according to arbitrary gradation data.

Here, the ON period of the reflection means is generally related to a period in which the light source device is in a light reflection state or the mirror element has a reflection surface oriented in a predetermined direction. In some cases, this ON period may be regarded as relating to a period in which the reflecting means exhibits a non-reflecting state, for example, an optical interrupting state. In this case, the result status is simply inverted.

(Driving circuit)

Hereinafter, the driving circuit used in the present invention will be described.

6 shows a driving circuit of the light modulation means indicated by C _LC .

It is first assumed that a sufficient voltage exceeding the threshold of the light modulation means (C _LC ) is applied while changing R _PC corresponding to any rating data. When R _PC is high, the time for which the voltage applied to C _LC exceeds the threshold value becomes faster. On the other hand, when the R _PC is low, the time at which the voltage applied to the C _LC exceeds the threshold value is accelerated. Thus, by adjusting the threshold exceeding time and the light emitting period of the light source, analog duty modulation of the transmitted light or reflected light becomes possible.

Fig. 7 shows a drive circuit different from the drive circuit shown in Fig. 6 only in that the light modulating means C _LC is connected in parallel with the resistor R _pc and the capacitance C _PC . In this case, a sufficient voltage Vd is applied for a predetermined period so that C _LC is in the ON state, and then a discharge phenomenon corresponding to the time constant of the RC circuit is utilized. In a high R _PC , which slows the discharge more slowly, the voltage applied to C _LC is delayed below the threshold. On the other hand, in a low R _PC that discharges faster, the voltage applied to the C _PC is lowered below the threshold value. By setting this time to the light emission period of the light source, the light transmission or reflection period can be modulated in an analog manner according to the time difference.

Fig. 8 shows another example of the drive circuit in which the gradation data is represented by the variable voltage Vv. 7, since the time constant of the RC circuit including R _PC and C _PC is fixed, the time required for the voltage applied to C _LC to drop below the threshold value is determined by the voltage Vv corresponding to the rating data . Thus, if this time is adjusted to the light emission period, the analog duty modulation is likely to be similar as in the example of FIG.

(Light source)

Will be described below with reference to a light source. The light emitted from the light source may be natural sunlight, white light, monochromatic light such as red, green, and blue light, and combinations thereof, and may be determined according to a suitable choice. Accordingly, the light source suitably used in the present invention may include a laser light source, a fluorescent lamp, a xenon lamp, a halogen lamp, a light emitting diode, and an electroluminescent device. These light sources can be turned on and off in a controlled manner in synchronization with the driving time of the light modulation means. In particular, the continuous irradiation time of the light source is preferably a maximum reciprocal flickering frequency (e.g., 1/60 second) which provides a visually detectable flicker. In the case of a color display, it is desirable to operate the R, G, and B light sources according to various time sequences to perform light modulation of R, G, and B according to time division. On the other hand, it is also possible to use a white light source in combination with a color filter to change the illumination light (wavelength range) using a filter of a different color for a time division.

(Optical modulator)

The light modulating device used in the present invention may include a light transmission type device called an optical shutter (or a light valve) and a reflective device as light reflecting means for modulating the light reflectivity. Typical examples thereof include spatial light modulation Light Modulation (SLM).

The optical shutter used in the present invention is capable of providing two optically different states. A preferable example thereof may be a liquid crystal element using liquid crystal as a light modulating material.

A preferred form of the liquid crystal device includes a liquid crystal disposed between a pair of electrodes. The liquid crystal molecules change the orientation state in accordance with the applied electric field, and the optical transmission through the liquid crystal molecules is a polarizing device. And is controlled according to the orientation state. Therefore, optical factors such as the transmittance, reflectance, transmission state, and reflection state of the liquid crystal device are determined in combination with the polarizing device.

More specifically, it is possible to use a liquid crystal cell (or panel) comprising a pair of substrates sealed with liquid crystals. At least one of the mutually facing inner surfaces of the substrate may be provided with a transparent electrode and an alignment film.

The substrate may be made of a transparent sheet such as glass, plastic or quartz. When constituting a device used as a reflection means, one substrate may be light impermeable. The transparent electrode is preferably made of a metal oxide conductor such as tin oxide, indium oxide or ITO (indium tin oxide).

The alignment film is preferably made of a polymer film, such as rubbing, which is subjected to coaxial alignment treatment, or an inorganic film formed by inclined deposition.

The liquid crystal may be suitably made of a nematic liquid crystal operating in a nematic phase and a smectic liquid crystal operating in a smectic phase. It is preferable to use a liquid crystal having storage characteristics such as chiral smectic liquid crystal or chiral nematic liquid crystal.

The reflection device used in the present invention is a DMD (Digital Micromirror Device) in which the reflective surface of the reflective metal is shifted by an electrostatic force caused by an applied voltage in order to change the angle of the reflective surface to modulate the direction of emission of the reflected light. Or a reflective liquid crystal device including a liquid crystal cell (or panel) as described above in which light incident thereon is reflected when the liquid crystal is placed in the light transmission state, one side being reflective and the other side being made transparent have.

Figures 9A-9D show some transmittance-applied voltage characteristics of optical modulation elements (materials) that can be used in the present invention. In the case of the DMD, the ordinate can be regarded as representing the amount of light reflected in a predetermined direction.

Figure 9A shows the characteristics of a light modulating material that causes the transition (switching) of the optical state when a positive threshold voltage is exceeded. Figure 9B shows the characteristics of a light-emitting material with positive and negative thresholds, respectively, with hysteresis. Figure 9C shows the characteristics of a light modulating material exhibiting hysteresis providing positive and negative threshold values. FIG. 9D shows a characteristic representing a threshold at a voltage of zero. Figures 9A-9D show characteristics in a somewhat simplified ideal form, and the vertical lines shown in these figures actually tilt to provide a threshold value and a saturation value on both sides, as shown in Fig.

9A or 9B is preferably combined with the parallel circuit shown in Fig. 7 or 8, and the characteristic of Fig. 9C or 9D is preferably connected to the series circuit shown in Fig. 6, .

The following Examples 1 to 5 are provided as reference examples for facilitating understanding of the present invention.

(First example)

10 illustrates an optical modulation system for driving an optical modulation device. This system comprises a liquid crystal element 101 including a pair of substrates each having an electrode on it and a chiral smectic liquid crystal disposed between the substrates, a gradation data generation circuit 103 for generating gradation data, and a light source 104 ). An observer 105 is displayed in front of this system.

The system also includes a capacitive element C _PC and a driver circuit including a transistor 102 in which a source-drain (or emitter-collector) resistance changes with a change in the gate or base potential of the transistor 102 Thereby changing the time point at which the voltage exceeds the inversion threshold value of the liquid crystal. This driving circuit includes a voltage applying means V _ext for applying a reset voltage and a driving voltage to the liquid crystal element. C _flc represents the capacitance of the liquid crystal.

The rating data generating circuit 103 includes a light emitting diode PED, four variable resistors VRB, VRG, VRR, and VRW, and four switching transistors TB, TG, TR, TW and a power supply VCC. The diode PED and the transistor 102 constitute an optical coupler.

The electric signal, which is a variable resistance value constituting the rating data for each color, is converted into optical data by the light emitting diode PED.

The light source 104 includes light emitting diodes EDR, EDG, and EDB that emit light of three colors (R, G, and B) and a variable resistor BR that is selectively used to take a white balance.

11 is a timing diagram of the system operation of Fig. 103T indicates a point of time when optical data is output. The curve V _flc in the FLC represents the voltage applied to the liquid crystal and the curve V _ext represents the voltage applied from the external power source V _ext . In _Tran , the transmittance level through the liquid crystal element is shown. And 104T indicates the output level of the light source. 105T shows the transmitted light amount level recognized by the observer 105. [

Referring to FIG. 11, first, white light for reset is supplied, and a reset pulse is applied from the voltage applying means V _ext , whereby the liquid crystal is once reset to the dark state.

Next, when the light corresponding to the R-grade data is outputted, the R light emitting diode

EDR is turned on and V _ext supplies a reverse polarity voltage to the liquid crystal element. During this period, the amount of R light from the PED is so small that the effective voltage applied to the liquid crystal does not exceed the threshold value Vth, and the liquid crystal element does not transmit the R light from the EDR.

Next, when the white light is supplied again, V _ext (voltage applied from the voltage applying means V _ext ) is increased so as to invert the liquid crystal to the light transmission state. However, at this time, no light source 104 is excited, and the observer can recognize the dark state continuously.

Next, V _ext is changed to a negative voltage, but the effective voltage applied to the liquid crystal does not exceed the -Vth threshold value, so that the liquid crystal element is maintained in the light state. However, also in this period, no light source is excited.

The R display period is ended in the above-described manner (in the embodiment of Fig. 11).

Next, the operation in the G display period is executed in a manner similar to that in the R display period. The data amount of G data is larger than that in the case of R described above, and the voltage applied to the liquid crystal exceeds the threshold value Vth at time trv. Next, during a period of time until the time t _off when the G light source EDG is turned off, the liquid crystal element transmits the G light to allow the observer to recognize the middle level of the G light.

Next, the operation in the B display period is executed in a manner similar to that in the R and G display periods. The amount of B data light is greater than in the case of G as described above and the voltage applied to the liquid crystal exceeds the threshold value Vth at time trv2. Next, during a period up to the time t _off2 when the B light source EDB is turned off, the liquid crystal element transmits the B light so that the observer can recognize the level close to the maximum level of the B light though it is at the intermediate level.

As described above, in this example, the V _flc time (point or period) exceeding the threshold value Vth is changed according to the rating data. Further, the time for turning off the light source is determined such that the light emission period of the light source does not overlap the transfer period (ON period) of the liquid crystal element corresponding to the gradation data giving the minimum level of the transmittance.

As a result, it is possible in this example to achieve the desired halftone level between the minimum level and the maximum level of luminance. Further, since the voltage applied to the liquid crystal is symmetrically adjusted with the positive and negative polarities, only the substantially zero DC component is applied to the liquid crystal to suppress deterioration of the liquid crystal element.

(Example 2)

12 shows another example of the light modulation system. The system includes a pair of substrates each having an electrode on its upper portion, a reflective liquid crystal element 201 made of liquid crystal disposed between the substrate, a light source driving circuit 204 for driving a light source, a capacitive element C _PC , R _PC , and a driving power source Vd. In this system, the circuit is configured so that the resistive element R _PC has a resistance value that varies depending on the input grade data.

The liquid crystal used may have a transmittance-applied voltage (T-V) characteristic as shown in Fig. 9A.

13 is a timing chart for driving the system of Fig. V _sl is the voltage applied to the application time of the voltage (Vd), V _lc is the liquid crystal, T _ran are respectively correspond to the reflectivity of the liquid crystal device, 204T is the irradiation time of the light source, 205T is on the level of the analog ratings data curve given by a low value of R _PC 1, m denotes a given curve and the reflected light quantity as possible by the observer including a curve n given by a high value of R _PC recognized by the intermediate value of R _PC.

Referring to Fig. 13, at time t _on , Vd is applied to the liquid crystal element, and the voltage _V1c applied to the liquid crystal becomes V1 sufficiently exceeding the threshold value Vth, so that the liquid crystal element exhibits the maximum reflectivity

do.

As the voltage Vd is removed at a time f, the voltage V _lC applied to the liquid crystal gradually decreases with the value of the resistance R _PC when the transmittance T _ran represents the lowest level, g., is lowered to below the threshold Vth at t _x3 for t _x2 for a time t _x1, m for one. In this embodiment, the light source as shown at 204T is designed to be turned on and turned off at time tx3 at time t _x1, the reflected light quantity 205T is the curve for the case of each of 1, m, of V _1c n 1, m , " n " By setting the irradiation time in this manner, linearity of excellent halftone display is given.

As described above, in this example, the V _lc time falling below the threshold value is changed according to the rating data. Further, the time for turning on the light source is determined so that the light emission period of the light source does not overlap the reflection period (ON period) of the liquid crystal element corresponding to the gradation data giving the minimum level of reflectivity.

As a result, according to this example, a desired intermediate reflection state between the minimum luminance level 1 and the maximum luminance level n can be achieved.

(Third example)

Fig. 14 shows another example of the light modulation system. This system comprises a pair of substrates each having an electrode on its upper portion, a reflective liquid crystal element 301 including a liquid crystal disposed between the substrate, a light source driving circuit 304 for driving a light source, a capacitive element C _PC , A resistance element R _PC, and a switch Vso for turning on and off the supply of the voltage signal from the driving power supply Vv and the driving power supply Vv. In this system, the voltage signal supplied from the driving power supply Vv carries analog grade data.

The liquid crystal used may have a transmittance-applied voltage (T-V) characteristic as shown in Fig. 9A.

15 is a timing chart for driving the system of Fig. Vso is the application time of the rating signal, V _1c is the voltage applied to the liquid crystal, T _ran is the reflectivity of the liquid crystal device, 304T is the irradiation time of the light source, 305T is at a lower voltage V1 to correspond to the level of the rating data A given curve 1, a curve m given by the intermediate voltage Vm and a curve n given by the high voltage Vn.

In Figure in relation to the 15, time t _on, Vv is the voltage V _1c applied to the liquid crystal is applied to the liquid crystal element is a voltage V1, Vm, and Vn, which sufficiently exceeds the threshold value Vth, respectively, the liquid crystal element is up to in any case As shown in FIG.

At time t _off, the voltage Vv is removed, whereby the voltage applied to the liquid crystal V _1c is, transmitters capacitance T _ran some time that depend on the ratings data to a gradual fall in response to a voltage Vv when represent the respective lowest level For example, t _x2 with respect to time t _xl and t _x3 with respect to n, which is lower than the threshold value Vth. In this example, a light source as indicated at 304T, are turned on at the time the turn-designed to be turned off at time t _x3, the reflected light quantity 305T curves for the case of one each of the V _1C, m, and n 1, m , ≪ / RTI > and n.

As described above, in this example, the time of V _1c descending below the threshold value depends on the rating data. Further, the time for turning on the light source is determined such that the light emission period of the light source does not overlap the reflection period (ON period) of the liquid crystal element corresponding to the gradation data giving the minimum reflection level.

As a result, it is possible to achieve the desired medium reflection state between the minimum brightness level 1 and the maximum brightness level n.

(Fourth example)

16 shows another example of the optical modulation system. The system includes a pair of substrates each having an electrode on its upper portion, a reflection type liquid crystal element 401 including an anti-ferroelectric chiral smectic liquid crystal disposed between the substrates, a light source driving circuit A capacitive element C _PC , a resistance element R _PC driving power supply Vv, and a switch Vso for turning on and off the supply of a voltage signal from the driving power supply Vv. In this system, the voltage signal supplied from the driving power supply Vv carries the analog grade data. The observer 405 is shown on the front face of the liquid crystal element 401. Fig.

The chiral smectic liquid crystal used may have a transmittance-applied voltage (T-V) characteristic as shown in Fig. 9B.

Fig. 17 is a timing chart for driving the system of Fig. 16; Fig. The Vso is the application time of the rating signal, T _aflc is the voltage applied to the liquid crystal, T _ran is the reflectivity of the liquid crystal device, 404T is to correspond to the irradiation time of the light source, 405T is on the level of the rating signal, a low voltage V1 The curve m given by the intermediate voltage Vm, and the curve n given by the high voltage Vn.

Referring to Fig. 17, Vd is applied to the liquid crystal element at time t _on , and the voltage V _aflc applied to the liquid crystal becomes V1, Vm, or Vn sufficiently exceeding the threshold value Vth, respectively, The maximum reflectance is exhibited.

At time t _off , the voltage Vv is removed, and the voltage V _aflc applied to the liquid crystal thereby gradually decreases in response to the voltage Vv, so that when the respective levels of _{thetransmittances} Tran become the lowest level, is time t _x1, falls to below the threshold Vth at t _x3 for t _x2, n for m for the first. In this example, the light source is designed to be turned off at the time the turn-on and the time from t _x1 t _x3 as shown at 404T, the reflected light quantity 405T curves for the case of each one, the V _aflc m, and n 1, m, and n.

It is preferable to set one cycle period (each of Prd1 and Prd2 in the cycle period 17 in FIG. 17) at a maximum of 1/30 sec and set the continuous irradiation time of the light source at a maximum of 1/60 sec or less.

This example differs from the embodiment of Figs. 14 and 15 in that an anti-ferroelectric liquid crystal is used and correspondingly the voltage Vv in the period Prd2 is inverted from that used in the previous period Prd1. Although the anti-ferroelectric liquid crystal can provide two threshold values due to the hysteresis of the opposite polarity, even if the polarity of the voltage Vv is inverted, the optical state of the liquid crystal is the same as shown in Tran. The chiral smectic liquid crystal exhibits a fast transfer speed (switching speed) between two molecular alignment states and can be selectively used in the present invention except for this embodiment.

As described above, in this example, the time of V _aflc falling below the threshold value is changed according to the rating data. Further, the time for turning on the light source is determined so that the light emission period of the light source does not overlap the reflection period (ON period) of the liquid crystal element corresponding to the gradation data giving the minimum level of reflectivity.

In the present invention, by using a two-dimensional extending device in which a plurality of optical modulating devices functionally equivalent to the optical transmitting device (optical shutter) or high reflecting device described in the above-described embodiment are arranged in a two-dimensional matrix, It is possible. It is also possible to use a planar light modulator having a two-dimensional extension portion in place of the two-dimensional matrix element, and each local region of the two-dimensional extension portion performs an equivalent function to the light modulator as described above.

More specifically, it is possible to use a panel having a DMD including a plurality of micromirrors arranged in a matrix and a two-dimensional extension portion in which a plurality of transmission type or light transmission type pixels are arranged.

Next, a driving method for an image display apparatus according to the present invention will be described.

18 is a cross-sectional view of an optical modulation device used in an image display apparatus according to an embodiment.

19A and 19B schematically show two molecular alignment states (optical states) of a chiral smectic liquid crystal used in the device. 20 is a graph showing electro-optical characteristics of a device including two optical states.

Before describing an embodiment of the present invention, the basic operation of the device shown in Fig. 18 will be described. 21 is a timing chart for explaining the operation of the apparatus.

The apparatus shown in Fig. 18 constitutes a so-called reflective liquid crystal panel. In the device, the transmissive substrate 511 is provided with a transmissive electrode 512, a photoconductive layer 513 as a light sensing layer, and a dielectric multilayer film 514 as a reflective layer successively on the transmissive substrate 511. The other transmitting substrate 516 is provided with a transmitting electrode 515. A chiral smectic liquid crystal (sometimes abbreviated as FLC) 517 is disposed as a light modulating material between these two substrates. And the polarizer 522 is also disposed on the light incidence side. Although not shown in the drawing, an alignment film for aligning the liquid crystal molecules is disposed at the boundary between the electrode 515 and the reflective layer 514 and the liquid crystal layer 517. The external voltage application means V _ext is connected to the electrodes 512 and 515 to apply a voltage between the electrodes. The device thus configured is illuminated with reset light 521, write light 518 carrying grade data, and read light 519 reading modulated grade data, i.e., an image.

The apparatus can be represented by an equivalent circuit shown in Fig.

Fig. 19A shows a first alignment state (optical state) of the liquid crystal molecules ML, and Fig. 19B shows a second alignment state (optical state) of the molecules ML. When the voltage + Vu is supplied to the liquid crystal in the first alignment state (Fig. 19A), the liquid crystal is switched to the second alignment state (optical state) (Fig. 19B). The resultant second alignment state (Figure 19B) is maintained even if the voltage is zero, i.e. not at all under an electric field. Next, if the reverse polarity voltage -Vu is applied to the liquid crystal, the liquid crystal is switched to the first orientation state (Fig. 19A), which is maintained even after the removal of the electric field. This switching can be referred to as transition or inversion of the liquid crystal. The first and second alignment states shown in Figs. 19A and 19B are all in a stable state, and therefore, the liquid crystal has a storage property.

Since the states shown in Figs. 19A and 19B are optically different states (different optical states), the polarizers can be properly combined so that one is placed in the maximum transmittance state and the other is placed in the minimum transmittance state. Here, the voltage value Vu is used to indicate a voltage exceeding the inversion threshold voltage and substantially the same saturation voltage.

Now, the operation of the device will be described. The capacitance C _flc of the liquid crystal layer 517 and the capacitance C _pc of the photoconductive layer 513 are equal to each other and the liquid crystal layer 517 has a large resistance of infinite in order to facilitate understanding of the working principle, 0.0 > 514 < / RTI > has an impedance of zero. Referring to FIG. 21, reference numerals 521T and 518T denote write light 518 having an intensity varying according to gradation data, illuminating the photoconductive layer 513 and the illumination time of the reset light 521 illuminating the photoconductive layer 513, Respectively. V _ext is to come denotes an AC voltage (alternating voltage) applied to the transmitting electrode (512 and 515) on both sides, V _flc represents an effective voltage applied by voltage division on both sides of the liquid crystal layer 517. + Vu and -Vu denote the voltages for causing the liquid crystal to invert from the first state to the second state and to invert from the second state to the first state, respectively, as shown in Fig. Tran shows the (first and second) alignment states of the FLC. In this embodiment, the lowest transmittance of the first alignment state (optical state) provides a dark state and the second alignment state (optical state) provides a bright state of the highest transmittance , The position of the polarizing element 522 functioning as both the polarizer and the decomposer is adjusted.

504T represents the irradiation time of the readout light 519 illuminating the liquid crystal layer 517 and 505T represents the output of the readout light 515T passing through the polarizer 522, the liquid crystal 514, the reflection layer 514 and the decomposer 522, Represents the level of light.

21, in the reset period from time t ₅₀ to t ₅₁ , V _ext (voltage supplied from power source V _ext ) is taken as voltage -V ₁ , and photoconductive layer 513 is illuminated with reset light, Thus, the optical carriers (electron-hole pairs) are generated in the photoconductive layer 513 and the electrons and holes are emitted from both sides of the liquid crystal layer 517 in the opposite direction according to the electric field applied to the photoconductive layer by voltage division Move. As a result of this operation, V _flc approaches the potential -V ₁ . As described on the basis of the equivalent circuit of Fig. 6, the voltage change is lowered by the photoconductivity effect that causes the resistance component of the photoconductive layer to cause self-discharge, As a result of the phenomenon that the potential provided to the photoconductive layer is lowered, it can also be understood that V _flc approaches -V ₁ . When the reset light has a superimposed optical intensity, V _flc can be reset to -V ₁ at time t ₅₁ regardless of the previous state, thereby ensuring the first optical state (dark) of the liquid crystal. At time t ₅₁ , the reset light is turned off and V _ext is changed to + V ₂ . At this time, the potential V _flc is changed to V ₃ = -V ₁ + [V ₂ - (- V ₁ )] / 2 by 1: 1 capacitance division. If no write light is provided as in the first period of this embodiment, V _fIc maintains V ₃ until t ₅₂ and the liquid crystal remains V ₃ V _U , thus maintaining the first optical state (arm) Next, in a period after t ₅₂ , an operation similar to the operation in the period of t _5o -t ₅₂ is performed while changing the polarity of V _ext . As a result, the integration of V _flc in one (cycle) period provides a DC component of zero, thus ensuring AC symmetry of the drive waveform required for stable FLC drive. In a period from t ₅₂ to t ₅₃ , V _flc is reset to V _l by exceeding Vu such that the liquid crystal is inverted to the second optical state ( _N )

In the second (cycle) period, the device is illuminated with write-in light. The write light has an intensity smaller than the reset light so that V _flc approaches V _ext with a slower time constant. When the writing light has a predetermined large intensity or a greater intensity, V _flc becomes V _u at time t _x1 within the period T (t ₅₁ to t ₅₂₎ when the liquid crystal is inverted from the first optical state to the second optical state .

If the write light has a larger intensity as in the third period, t _x1 is closer to t ₅₁ so that the liquid crystal is inverted to the second optical state in a more correct time. In each of the second and third cycle periods, a write light similar to that used in the period of t ₅₁ to t ₅₂ is supplied within a period of t ₅₃ to t ₅₄ (i.e., t _{50 in the} subsequent cycle period), and V _flc Falls below -V _u at time t _x2 , whereby the liquid crystal returns to the first optical state (arm). At any of the first through third periods, AC _{fl ash} symmetry is assured, and in each period the liquid crystal takes the first optical state and the second optical state for 50% of each period. As the write light intensity increases, the second optical state of the FLC is phase-shifted faster.

In parallel with the liquid crystal state change, the read light is supplied in the period from t51 to t52 in each cycle period, and the observer recognizes the output light only during the overlap period between the light emission period of the readout light and the second optical state do. As a result, no output light is given in the first cycle period, but the output light flux is increased as the write light intensity is increased to provide a longer overlap period, such as in the second and third cycle periods. If each cycle period is set to be shorter than a period (e.g., 1/60 second) of the minimum frequency (i.e., a flickering frequency of, for example, 60 Hz) giving a recognizable flicker to the human eye, As the intensity changes, the change of the output light flux is recognized by the observer.

On the other hand, if the reading light is supplied in the period of t ₅₃ -t ₅₄ instead of the period of t ₅₁ -t ₅₂ , the overlap period is reduced to reduce the output light reflux (reflux) as the write light intensity is increased . Thus, a negative-positive exchange between the write-in light and the read-out light becomes possible. The write light is provided in a two-dimensional plane spreading form so as to be able to form a planar potential distribution according to the write light intensity, thereby providing a so-called write-in type spatial light modulator allowing two-dimensional light writing and reading .

22 is a system diagram of a full-color film viewer as an image display device including an optical-write spatial light modulator as described above.

The writing-side light source includes light-emitting diodes (LEDs) of three colors of R, G,

22, reference numeral 530R denotes an R-write light source LED, 530G denotes a GV write light source LED, 530B denotes a B-write light source LED, 535 ) Denotes a reset light source, and reference numeral 531 denotes a three-color mixing prism having an R reflection surface and a B reflection surface. The system further includes optical modulation elements, lenses 532 and 534, a film 533, and a prism 537. The system further includes a readout light source system including R readout light source LED 539R, G readout light source LED 539G, B readout light source LED, and a tri-color mixing prism having an R reflection surface and a B reflection surface.

The system operation of Fig. 22 will be described with reference to Fig.

Each cycle period is set to be at most about 5 msec (= 1 / flickering frequency / 3).

The write light sources 530R, 530G and 530B are sequentially turned on for each one cycle period. On the other hand, the reading light sources 539R, 539G, and 539B are sequentially turned on concurrently with the writing-side light source. The film 533 carries image data taken to include the rating data represented by the transmittance of 0% for R, 50% for G, and 100% for B, respectively.

During three cycle cycles, additional color mixing is performed to provide full color output.

As previously described, by changing the illumination time for the read-out light source, the system can be applied to the amniotic membrane or membrane as the membrane 533.

If a transfer type liquid crystal TV having a color filter is used in combination with a color rotation filter and a halogen lamp as a light source as a light source instead of the film 533, the system can provide a motion picture projector.

Incidentally, in the case of constituting a monochromatic OHP (overhead projector) including monochromatic writing, for example, the reset light source may be omitted if the amount of write light for a specific pixel area is not changed.

If the reset light source has at least a predetermined intensity, it is thereby layered, so that writing can be performed in an overlapping fashion within the reset period without causing a problem.

Another example of the phototyped film viewer will be described with reference to FIG.

The optical system constituting the image display apparatus according to these embodiments is the same as that shown in Fig. 22, and the optical modulation element has the structure shown in Fig. 18, and therefore, another description thereof will be omitted.

24 is a timing chart for driving an image display apparatus including the light modulation device shown in Fig.

The basic operation is the same as that of the embodiment of FIG. 21, except that the write light 518T is supplied only in the period t ₆₁ -t ₆₂ in the cycle period, that is, in the former half of the write period and in the remaining period The latter half). The light supplied in the period of t ₆₁ -t ₆₂ does not contribute to the reading. On the other hand, the uniform bias light 550T is supplied within the period of t ₆₂ -t ₆₃ , that is, at the rear half portion of the writing period. When the writing light 518T carrying the rating data is zero as in the first cycle period, the voltage applied to the liquid crystal is constant at -V ₆ through the period of t ₆₁ -t _62. Next, when the bias light (550T) is supplied from the time t _62, the voltage V _flc applied to the liquid crystal is due to the resistance drop in the photoconductive layer 513 is increased by an amount direction. In this example, the value of R _PC or C _pc (FIG. 6) and the time t ₆₃ are adjusted so that the voltage V _flc does not exceed the threshold of the liquid crystal (+ Vu) even at time t ₃ if the write light is at the minimum level . Therefore, when the write light is 0, that is, the minimum level, the output light 505T is also 0, that is, the minimum level. In the period from t _{63 to} t ₆₀ in the subsequent cycle period, the liquid crystal is inverted by application of a positive polarity voltage. In this period, no reading light is supplied, so that no image data is reproduced or outputted.

In the writing light is the intermediate level, the second cycle period, the photoconductive layer 513 is caused to have a low resistance, the liquid crystal is higher than the supply voltage -V ₆ in an amount direction,

In the period t ₆₂ -t ₆₃ of the second cycle period, the bias light 550T is similarly supplied, and the voltage V _flc applied to the liquid crystal is different from the first cycle cycle t ₆₂ -t ₆₃ when the reading light is supplied in in the medium in time t _x1 is increased to exceed the threshold (+ Vu) of the liquid crystal from the high initial voltage higher than -V _6. As a result, when the readout light is reflected by the reflective layer 514 of the element, it exhibits the maximum transmittance Tran in the period of liquid crystal t _x1 -t ₆₃ . Therefore, the period for reflection of the readout light is modulated in accordance with the write light amount 518T. The remaining time after time t ₆₃ is used for an inverting operation similar to that within the first cycle period.

In the third cycle period, the maximum level of write light is supplied (518T), so that the voltage V _flc applied to the liquid crystal is already at the critical point t ₆₂ at the beginning of the period t ₆₂ -t ₆₃ for the bias light source, Value + Vu. Therefore, during the entire period of t ₆₂ -t ₆₃ at which the reading light is supplied, the liquid crystal shows the maximum transmittance. As a result, the time integral of the amount of reflected light of the reading light incident on the device and reflected in the prescribed direction becomes the maximum.

As described above, the readout light reflection time is determined according to the amount of write light, so if the write light amount is changed in an analog manner, the reflection time is changed in an analog manner in accordance with the change of the write light amount.

In the period of t ₆₃ -t ₆₀ for the inversion operation of each cycle period, the polarity of the applied voltage V _ext is inverted, and the write light and the bias light are supplied in the same amount of light as in the writing period. As a result, the time integration of the effect voltage applied to the liquid crystal in one cycle period becomes 0, and deterioration of the liquid crystal is suppressed accordingly.

In this example, the level of the bias light amount can be suitably determined in terms of the time constant of the photoconductive layer 513 and the period length of t ₆₀ -t ₆₃ . The light source of the bias light may be the same as or different from the reset light source. However, it is preferable that each of the bias light source and the reset light sources is provided with dimmer means so as to allow the amount of light to be independently controlled.

In this example, if each cycle period is set to be about 1/30 second or less and the period of t ₆₀ -t ₆₃ is set to about 1/6 of a second or shorter, a good halftone display without flickering display may be possible.

In this example, the previous example is modified so that the read and write light sources are replaced by three color light sources that are independently driven R, G, and B, respectively, wherein the first cycle period is assigned as the write and read cycle for R, The second cycle period is assigned to write and read cycles for G, and the third cycle cycle is allocated to write and read cycles for B, whereby image reproduction according to full color light modulation is performed.

25 is a timing chart for driving an image display apparatus including a light modulation element according to still another example.

The default behavior is different from the point is replaced by increasing the voltage V _ext applied to the device in a period of the same, and a bias light illumination T ₇₂ -T ₇₃ as the preceding embodiment of Fig.

In a period of t ₇₀ -t ₇₁ , reset light is supplied (721 T). At this time, V _ext is zero.

In time T71, V _ext is the voltage applied to the liquid crystal but the change in threshold value + Vu of the liquid crystal V _flc is a lower voltage + when the writing light (718T) applied to the photoconductive layer 513 which is the minimum level (= 0) Vuu. When the photoconductive layer 513 and the liquid crystal layer 517 have the same capacitor, + Vuu becomes equal to Vu / 2.

At time t ₇₂ , when the write light 718T goes to zero, the voltage V _ext applied to the device increases gradually to + Vem over time at time t ₇₃ . Accordingly, the voltage V _flC applied to the liquid crystal is increased.

At this time, if + Vem is set to be twice as much as + Vu, V _flc reaches + Vu at time t ₇₃ . As a result, in the period t ₇₂ -t ₇₃ , the liquid crystal does not cause switching of the optical state, and thus does not exhibit the maximum transmittance state while the readout light remains on (704T).

The remaining period of t ₇₃ -t ₇₀ is for the inversion operation while the image reproduction is not performed because the reading light is not supplied.

In the second cycle period, intermediate level write light illumination is performed (718T). As a result of the previous inversion operation, the liquid crystal is placed in a non-light-transmissive state at time t _{70. When} V _ext is O, V _flc approaches a voltage level of O.

At time t1, _Vext becomes equal to the threshold + Vu, and the read light is turned on (704T). As a result of applying V _ext , V _flc is increased but does not reach the threshold + Vu.

At time t ₇₂ , V _ext begins to increase, so that it can be increased beyond the threshold value + Vu at time t _x1 when the liquid crystal is switched to the optical state representing the maximum transmittance. Thus, at this time t ₇₂ , the read light already turned on is incident on the reflective layer 514 through the liquid crystal layer 517 and is allowed to be reflected there to provide a recognizable reflective image. Thus, the reflection time t _x1 -t ₇₃ is modulated depending on the writing light quantity. The period after time t ₇₃ is for reversal operation.

In the third cycle period, write light is supplied at the maximum light amount level. Operation within the period of t ₇₀ -t ₇₁ is the same as operation of the first and second cycle periods described above.

After illuminated by the writing light started at time t _71, V _flc reaches the threshold + Vu at time t to _72. Thus, during the readout light emission period of t ₇₂ -t ₇₃ , the liquid crystal remains in optical state, which is the maximum transmittance, so that the readout light can be reflected by the device for a maximum period of time (705 T).

As described above, the readout light reflection time is determined according to the write light amount, and therefore, if the write light amount is changed in an analog manner, the reflection time is changed in an analog manner along with the write light amount change.

In the period of t ₇₃ -t ₇₀ for the inversion operation of each cycle period, the polarity of the applied voltage V _ext is inverted, and the writing light and the bias light are charged to the same light quantity as in the writing period. As a result, the time integration of the effect voltage applied to the liquid crystal in one cycle period becomes zero, and deterioration of the liquid crystal is suppressed accordingly.

In this example, a change with time of V _ext can be suitably determined in terms of the time constant of the photoconductive layer 513 and the length of the period of t ₇₁ -t ₇₃ .

In the present, if each cycle period is set to about 1/30 second or shorter than, good halftone display again if the period of t ₇₀ -t ₇₃ of about 1 / 6O seconds or set to be shorter than without flickering May be possible.

(Embodiment 1)

Now, a first embodiment of the present invention will be described. In the reference example referring to Fig. 22, a two-dimensional image carrying a graded data on a film or the like is written to the photoconductive layer of a liquid crystal device which is an optical firing device fundamentally by a single write light illumination. In this embodiment, the two-dimensional image is written to the liquid crystal device sequentially in time by vertical and horizontal scanning. The written grade data can be read by similarly scanning the liquid crystal device using readout light at an appropriate timing.

26 is a schematic plan view of a reflection type liquid crystal device 801 having a photoconductive layer and a chiral smectic liquid crystal layer having the same structure as shown in Fig. 18 to explain a scanning method. The liquid crystal device is scanned using the horizontal scanning writing light 802 while gradually shifting the horizontal scanning light down in a non-interlaced manner similar to the normal scanning on the CRT. In other words, the photoconductive layer is sequentially irradiated or illuminated with writing light in time. On the other hand, the reading light 803 is caused to illuminate the portion of the liquid crystal layer corresponding to the writing position of the photoconductive layer only for a prescribed period to reproduce the rating data. Thus, illuminating the device with readout light is also performed in time sequence. Scanning with the reading light 803 is performed after scanning with the writing light 802. [

Fig. 27 is a block diagram of a CRT (cathode ray tube) 810 as a writing light source, an image forming lens 811, a reset light source 812, a mirror 813, a polarizing beam splitter 814, a movable mirror 815, The image display system corresponding to this first embodiment, including the illumination filter 816, the reading light source 817, the illumination lens 818 and the image reproduction screen 819. [

The reading light scanning means may be configured by a combination of a fixed mirror and a movable light source 817 or a combination of a movable mirror and a movable light source instead of the movable mirror 815. [

Further, the writing light source is not limited to a CRT and can be constructed using a movable mirror or a movable light source like the reading light scanning means. In order to write a high resolution image, it is desirable to use a write light source that allows two-dimensional scanning of the light beam, such as a CRT.

Reset light source 812, lens 811, filter 816, etc. may be used as described and may be omitted.

(Second Embodiment)

28 includes a plurality of write light illumination means 810-812 and a plurality of optical modulation devices 801. The read light is divided into spectrums by mirrors 813R, 813G and 813B, ≪ / RTI >

In such a system, white light may be incident on individual light modulating devices 801, for example, R, G, and B, to take reflected light that is individually modulated by the optical data written to the individual light modulating device 801 Light. In this case, the readout light source may also be divided into a plurality so that it can be assigned to each write light source, and the light modulation devices provided for the individual colors are illuminated by writing and reading light for each color.

In the case of using a white light source, the scanning timing of the readout light is performed simultaneously for the individual colors so that images without color deviations can be obtained. On the other hand, when using a read-out light source for individual colors, the individual color light sources can be independently controlled to facilitate adjustment of the color balance.

29 is a time chart illustrating the above-described first embodiment or the second embodiment in more detail. In the embodiment of Fig. 21, operation of three cycle periods is described, while Fig. 29 illustrates operation of one cycle period.

Reference numeral 821 shows the operation of reset light similar to that of reference numeral 521 in Fig.

In the period t ₈₀ - t ₈₁ , the reset light illuminates the light modulation device.

The waveforms of reference numerals 818 T1, 8201, Tran1 and 504 T1 are shown to illustrate the operation of the first picked-up first by write-in light 802 in accordance with non-interlaced scanning.

Reference numeral 818T1 shows the operation time of the write light 802 incident on the first pixel.

At time t ₈₁₁ , when the first pixel is illuminated with write-in light 802, electron-hole pairs having an electric charge Q that is proportional to the write light intensity are generated to cause a potential change DELTA V = DELTA Q / (c) do. In a stronger write light intensity, V _flc exceeds Vu in a short time to cause a change in light state of the FLC from a dark state to a bright state. In other words, a write light intensity-FLC phase conversion is performed .

FIG. 29 shows the case where the write light is transmitted to the maximum intensity so as to achieve the maximum light quality, when the write light is transmitted to the predetermined offset light intensity to provide the dark display state, The write light is transmitted to the intermediate light intensity.

As shown in Tran1, FLC is written if the light is from the time tx _1l1 case is transmitted to the maximum intensity, and the writing of the light-minimum level transmitted to the predetermined offset light intensity is a second optical state (bright state) at the time tx ₁₁₃ Causes a state change to

Reference numeral 504T1 shows the operation of the readout light incident on the first pixel. When the first pixel period t ₁₁₁ to t ₁₁₃ illuminated by a reading light for the observer can recognize the light during overlapping periods between the FLC of the second optical state (bright state) and a read light illumination time period. If writing in the first pixel and reading therefrom is repeated for a shorter cycle period than corresponds to the flickering frequency, then the overlap period variation is recognized by the observer as the light intensity change of the first pick-up.

As described above, reference numerals 818Tn, 820n, Tran n, and 504Tn are shown to illustrate the operation of the n-th pixel located at the approximate center point of the image area written by the non-interlaced scanning mode.

In addition, the waveforms of reference numerals 8181TN, 820N, Tran N, and 504TN are shown to illustrate the operation of the Nth pixel written last with write light 802 by non-interlaced scanning.

Together operation of the individual pixel is similar to the operation of the first pixel, in which case the n-th pixel is written at the time t _8ln, the N-th pixel is written at the time T _81N.

After being illuminated by the reset light, the device 801 is scanned with the write light 802. At the same time, the device 801 is sequentially supplied with the reset voltage and the write voltage. As a result, the liquid crystal is supplied with an effctive voltage that changes with time in accordance with the quality of the illuminated light due to the light absorption by the photoconductive layer, so that the liquid crystal has a different point in time at which the effect voltage exceeds the threshold value To provide a time of another period in which the liquid crystal is placed in the reflective state according to the given rating data. When properly overlapping with the time of the reflection state, the liquid crystal is scanned with the reading light 803. In this embodiment, scanning is performed by movement of the movable mirror 815. [ More specifically, when the movable mirror 815 is moved in the direction of the arrow AA, the reading light 803 illuminating the device 801 moves in the direction of the arrow AA on the liquid crystal device, Type reading light. One horizontal scanning period of the reading light 803 can be set to 1/60 second or shorter thus allowing halftone recognition. The scanning movements of the movable mirror 815 and the CRT 810 are controlled Are synchronized with each other by a circuit (not shown). It is particularly preferred to control the light source and the scanning means to perform only during _x113 t - is the light and / or illumination synchronous modulation can _xl11 period t which is determined by the rise time. The photoelectric characteristics of the light modulator 801 cycles ₁₁₁ t - may preferably be determined so as to set up to 1/60 sec t _x1l3.

The operation of the optical modulator to implement the grading data may be performed in accordance with the principles described with reference to Figures 1 - 25, and more particularly with reference to Figures 11, 21 and 23 - 25 have. Therefore, the driving method described with reference to the drawings can be combined with the scanning of the readout light and the write light described with reference to FIGS.

The above-mentioned second embodiment is a modification of the first embodiment so as to be applicable to a full-color display, whereby the writing light scanning means and the liquid crystal device 801 are arranged in a separate color, for example R, G and B Available in two sets for three colors (800R, 800G and 800B).

The operation of the system shown in Fig. 28 is basically the same as that described with reference to Fig. 29 for the system of Fig. If the write light scanning timing is synchronized for the three colors, a full color display is possible with additional color mixing. The display device thus constructed is suitable for full color moving picture display and is therefore suitable for use in large screen size television system configurations.

(Third Embodiment)

Although the first and second embodiments described above are described as using a non-interlaced scanning mode using spot beams of write light similar to those in CRTs, for example, linear or 2 < RTI ID = 0.0 > It is also possible to perform the linear sequential writing method by using the dimension LED array.

(Fourth Embodiment)

Fig. 30 is an equivalent circuit diagram of a liquid crystal device used in this embodiment of the present invention, and Fig. 31 is a partial cross-sectional view covering approximately one pixel of the device shown in Fig.

The apparatus according to this embodiment is an active matrix type liquid crystal device including a switch TFT, a resistance element Rpc and a capacitive element Cpc for each pixel, and also includes N gate lines (scanning lines) G ₁ -G _N and M And an electrode matrix composed of source lines (data lines) S ₁ - S _M. 31, the apparatus is provided with functional elements on a transparent substrate 901, and a liquid crystal layer 904 is sandwiched between a corresponding transparent substrate 902 carrying a common transparent electrode and a substrate 901, .

Each of the switch TFTs includes a gate electrode 906, a gate insulating film 908, a channel layer 914, ohmic layers 910 and 909 individually constituting a source and a drain, and source and drain electrodes 911 and 912. [ 912).

The capacitive electrode element Cpc includes a drain electrode 912, an ohmic layer 909, an insulating film 908, and a bottom electrode 907.

The resistive element R _pc includes a drain electrode 912, an ohmic layer 909, and an electrode 913.

The gate electrode 906 and the bottom electrode 907 may be deposited in a common step to form a patterned conductor and the channel layers 914 and 915 may be deposited in a common step to form a patterned semiconductor.

Gate electrodes 906 are connected in common for each row to provide gate lines G ₁ -G _N and source electrodes 911 are commonly connected for each column to provide source lines S ₁ -S _M do.

The common electrode and the lower electrodes 907 for all the pixels are commonly connected to the reference power supply and held at the reference potential.

32 is s a timing chart for illustrating the operation of the liquid crystal device and the source line S ₁ -S _M there is a signal having a voltage changing in time sequence corresponding to the rated data supplied in parallel to the gate lines G ₁ - G _M Are sequentially supplied with signals for turning on the switch TFTs to perform multiplex driving.

The reading light illuminates a row of pixels during the period P _ON to perform scanning to follow the gate-on signal.

The principle of the grade display is the same as the principle described with reference to Fig.

When the gate-on signal is supplied, the switch TFT is turned on to supply the level signal voltage through the switch to raise the potential of the drain electrode 912 functioning as the pixel electrode. Due to the potential difference between the pixel electrode potential and the potential of the common electrode 903, the liquid crystal 904 is molecularly oriented in the light transmission state. The electric charge of the pixel electrode is discharged through the ohmic layer 909 as the resistive element R _pc , so that the electric potential of the pixel electrode 912 becomes gradually lowered. When the potential drops below the threshold, the liquid crystal molecules are oriented in a light interrupted state.

The time at which the potential falls below the threshold depends on the voltage applied to the source line and also on the time constant given by resistive element R _pc and capacitive element C _pc . Simultaneously with the modulatable range of the liquid crystal period that is in the optical transmission state, the pixel is illuminated with readout light for a prescribed period (e.g., 1 / 60x a second). The readout light may be in the form of a stripe and may be moved to be scanned vertically to read one frame of image data.

If a pixel on the n-th row are taken by way of example, to the pixels, the time rating signal is supplied from the t _n, and, also the pixels corresponding period is elapsed after a time lights in t _on the read-out light to the multiple of the horizontal scanning period Initiation and ceasing to be illuminated at t _off are abrupt.

The resistive element and the capacitive element used in the present invention are not limited to those shown in Figs. 30 and 31.

The gate electrode 906 and the source electrode 911 may comprise a metal such as Al, Cr, Cu, Mo, W, or Ta, or an alloy of these metals. The pixel (drain) electrode 912 and the bottom electrode 907 may comprise a transparent conductor such as ITO, SnO ₂ or InO.

The gate insulating film 908 may preferably include an insulating material such as SiN, SiO, Ta ₂ O _3, or Al ₂ O ₃ . The channel layer 914 may preferably include amorphous silicon, including high-resistivity non-single crystal silicon.

The ohmic layers 909 and 910 may be formed of low resistance amorphous silicon (including non-monocrystalline silicon) doped with atoms selected from the atoms belonging to Group V of the periodic table, microcrystalline silicon, Can be included.

Figure 34 shows an image display device 900 including a liquid crystal device 900 as described above and also including a read light source 817, a movable mirror 815, a lens 818, a screen 819 and a stop 831. [ / RTI >

Readout light is converted to a striped flux having a defined width through a stop 831 and is moved to a movable mirror 815 to illuminate the device 900 while following the movement of the turned on gate line, And is moved and scanned.

Claims (33)

A pair of electrodes, a photoconductive layer and a layer of optical modulator disposed between the electrodes, a signal light source for supplying optical data carrying graded data to the photoconductive layer, and a readout A method of driving a display device including a light modulator having a readout light source for supplying light to the light modulating material layer, the method comprising: scanning and supplying the light data to the photoconductive layer; And scanning and supplying the read light to the optical modulator layer. 2. The method of claim 1, wherein the photoconductive layer is supplied with the optical data according to a horizontal scan, and then a corresponding portion of the optical modulator layer is scanned with the readout light. Way. The method of claim 1, wherein the signal light source supplies at least two types of optical data having different wavelength ranges. The method of claim 1, wherein the signal light source supplies red, green, and blue light data. 2. The method of claim 1, wherein the display device includes a plurality of signal light sources and a corresponding number of light modulation devices. 2. The method according to claim 1, wherein the reading light is scanned by a movable mirror. The method according to claim 1, wherein the reading light is divided into a spectrum by a mirror that selectively transmits or reflects light of a predetermined wavelength. The method of claim 1, wherein the display device includes a CRT, a movable mirror, and a polarizing beam splitter. The display device driving method according to claim 1, wherein the optical modulator is supplied with reset light before supplying the optical data. The method of claim 1, wherein a write voltage is applied between the pair of electrodes after a reset voltage of one polarity is applied. The optical modulator as claimed in claim 1, wherein the optical modulator comprises a plurality of scanning lines and a plurality of data lines intersecting the scanning lines, each corresponding to an intersection of the scanning lines and the data lines, And a matrix of pixels including a photoconductive layer and a light modulating material between the electrodes is formed. 12. The method of claim 11, wherein a reset voltage is simultaneously supplied to the pixels on all of the scanning lines. 12. The method according to claim 11, wherein reset light is simultaneously supplied to the photoconductive layer corresponding to the pixel or all the scanning lines. 2. The method according to claim 1, wherein the reading light is supplied to a pixel during a period during which the light modulating material in the pixel can change its optical state. 2. The method according to claim 1, wherein the light modulating material changes an optical state at a time when the optical modulating material changes in accordance with optical data supplied within a period for supplying the reading light. 12. The method of claim 11, wherein one horizontal scanning using readout light is performed in synchronization with one horizontal scanning using the optical data. 2. The method according to claim 1, wherein the light modulating material comprises a liquid crystal having storage characteristics. The method of claim 1, wherein the light modulating material comprises a chiral smectic liquid crystal. 19. A method according to any one of claims 1 to 18, characterized in that the irradiation time of the read-out light source is controlled to modulate the overlap period between the period of the light modulating material having the prescribed optical state and the irradiation period according to the given grade data To the display device. (a) a plurality of two-dimensional pixels each including a light modulation element formed by positioning a layer of light modulating material between a pair of electrodes and a driving element for supplying an electric signal carrying gradation data to the light modulation element, (B) a readout light source for supplying readout light for reading image data to the layer of optical modulation material, the method comprising the steps of: To a selected pixel; Scanning the pixels with the readout light to supply the readout light to the light modulating material of the selected pixel; And Controlling the irradiation time of the read-out light source to modulate an overlap period between the period of the light modulating material having the prescribed optical state and the irradiation period according to the given grade data. 21. The method of claim 20, wherein an electrical signal is applied to one horizontal pixel row comprising the selected pixel, and then the pixel row is scanned with the readout light. 21. The method according to claim 20, wherein the driving element includes a transister. 21. The method of claim 20, wherein the driving element comprises a transistor and a resistive element. 21. The method of claim 20, wherein the driving element comprises a transistor, a resistive element, and a capacitive element. 21. The method of claim 20, wherein the reading light is illuminated for a period longer than the scanning selection period of the pixel. 21. The method of claim 20, wherein a time point at which the voltage applied to the optical modulator falls below a predetermined value is modulated. 21. The method of claim 20, wherein the driving element comprises a transistor connected to a pixel and having a source, a gate and a drain, and the electrical signal is supplied to the source. 21. The method of claim 20, wherein the reading light is supplied to a pixel during a period during which the light modulating material within the pixel is capable of changing its optical state. 21. The method according to claim 20, wherein the light modulating material changes an optical state at a time when the optical modulating material changes in accordance with optical data supplied within a period for supplying the reading light. 21. The method of claim 20, wherein the light modulating material comprises a liquid crystal having storage characteristics. 21. The method of claim 20, wherein the light modulating material comprises a chiral smectic liquid crystal. The method according to any one of claims 1 to 18 and 20 to 31, wherein the reading light is continuously supplied for a period of a maximum of 1/30 second. The method according to any one of claims 1 to 18 and 20 to 31, wherein the reading light is continuously supplied for a period of a maximum of 1/60 second.